When I picked mine up about 2 years ago from Ft. Rucker, it had about 3/4 of a tank of diesel that had been in for who knows how long. Coming out the front gate, my buddy in chase asked me how the truck was running. I told him that it was running strong and fine. He informed me of all the white and grey smoke coming out the stack. A little history on old diesel's told me the fuel was probably junk but fortunately a multi will burn stuff most motor's will choke on. We made it about 100 miles before the truck stalled while coming to a stop. The primary fuel filter was full of water. After a drain and prime, we were back under way and we burned the rest of that fuel out without issue. I'd bet the hard constant 50 to 55 mph run coupled with some new fuel towards the end cured that mess. Of course, I've since changed to a spin on primary fuel filter and have run a few hundred gallons of diesel through it as well. Sounds normal to me, drive the truck and give it H#$$.